Ab Initio Investigations of Iron-Based Martensitic Systems

We apply a full-potential first-principles method to investigate the electronic-structure and elastic features of pure iron and ordered transition metal systems like Fe-Ni and Fe-Mn. The martensitic phase transformations in these compounds mainly depend on the properties of iron. Therefore the phase diagram of iron has been studied in detail in view of structural transformations and magnetic order. To this the total energy and magnetic moment have been investigated as function of the atomic volume. In agreement with experimental results, we find a ferromagnetic bcc ground-state and an antiferromagnetic fcc phase having a higher energy of 7 mRy. The resulting pressure for the bcc → hcp transition is about 11.5 GPa in agreement with experiments. Besides that, total energy calculations have been done for stoichiometric Fe-Mn and Fe-Ni compounds. The resulting alloy phase diagrams are in a good agreement with the experimental data